Method and arrangements relating to satellite-based positioning

Abstract

A method, an apparatus and a computer program for determining a location at which satellite ranging signals (RS1-RS 4) have been received. At least one pseudorange selection cycle (511, 512), including an initial selection cycle (511), is performed and said location is determined utilizing the selected pseudoranges (1004). Said initial selection cycle includes: determining a first admissible pseudorange (r11) associated with a first satellite (SV1); determining (502) all pseudoranges (r21, r22, r31, r32) associated with at least two additional satellites (SV2, SV3) which combined with said first pseudorange (r11) form admissible relative pseudoranges; forming (503) a set (1001) of pseudorange vectors representing all possible combinations of said determined pseudoranges (r11, r21, r22, r31, r32) associated with said first (SV1) and at least two additional satellites (SV2, SV3); and forming (504) a set (1002) of selected pseudorange vectors by selecting at least one vector from said set (1001) of pseudorange vectors. At least when said set (1001) of pseudorange vectors includes plural vectors, said selecting includes evaluating each vector in said set (1001) of pseudorange vectors according to a predetermined rule.

Description

TECHNICAL FIELD OF THE INVENTION [0001] The present invention relates in general to positioning of mobile equipment by use of satellites and in particular to such positioning assisted by land based communication nodes. DESCRIPTION OF RELATED ART [0002] In recent years, determination of the geographic position of an object, equipment or a person carrying the equipment has become more and more interesting in many fields of application. One approach to solve the positioning is to use signals emitted from satellites to determine a position. Well-known examples of such systems are the Global Positioning System (GPS) (see e.g. [1]) and the coming GALILEO system. The position is given with respect to a specified coordinate system as a triangulation / trilateration based on a plurality of received satellite signals. [0003] A stand-alone GPS receiver can obtain full locking to GPS satellite signals, without having any other information about the system except nominal carrier frequency and the ...

AI Technical Summary

Benefits of technology

[0010] Another advantage of the invention is that the increased robustness is achieved without reducing the detection sensitivity.

[0011] Yet another advantage of the invention is that the increased robustness is achieved with an insignificant increase in processing delays.

Problems solved by technology

The inventor of the present invention have identified a problem with AGPS in that measuring and reporting truncated timing of received ranging signals may cause ambiguities when determining pseudoranges to space vehicles, if the precision of the apriori information about the mobile station position is too low, i.e. the uncertainty of the mobile station position in said apriori information is too large.

As a result, if an incorrect pseudorange is selected and used as a basis for determining the location of the mobile station, there will be a significant error in the calculated mobile station position in the order of e.g. 100 km.

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